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Thread: Tandon PAC 286 HDD Trouzble

  1. #1

    Default Tandon PAC 286 HDD Trouzble


    iĀ“ve recently aquired the machine above and i have at least two problems with it.

    First problem are the Datapac Drives, which are connected to a Tandon Specific RLL 16 Bit ISA controller. Sometimes they fail more or less immediate when the Machine is powered on (DatapacĀ“s Green LED start to flash, Motors turn off) , sometimes, after a long seek while performing the memory Test , they stay on, but they are not always recognized correctly at all.

    This machine generally offers some kind of Boot menu and, if a HDD stays on, i could choose one of the Datapacs to boot from (the Boot Menu even shows the Label of the HDD), but of course nothing happens.

    So far iĀ“ve managed to boot from a FDD which includes Speedstor, in order to try to perform a LowLevel-Format on the HDDs, but SSTOR dosntĀ“get alyways the Drive Parameters correct (so i have to choose them manually) and SSTOR is even is unable to LL-Format those drives at all; it fails with a "Controller response error". Controller Diagnostics within SSTOR tells me that there is even a Controller Failure . My suspicion is that SSTOR isnĀ“t able to handle this type of Controller at all or something else blocks, but i cannot figure out the Problem. DOS FDISK wonĀ“t find any HDDs at all.

    Maybe the Controller provides at least at some sort of Extra-Functions which can be only accessed by the Tandon-Specific DOS-Tools, but since i doĀ“t have any Disks got with this machine and i am unable to find any Source, iĀ“m stuck now where i am. I doubt that the drives themselfes are "too defect to work properly", My suspicion is that there is some kind of surface magnetization faul and the controller tries to read the surface after switching the Machine on and fails if some information could not be obtained properly.

    Replacing the controller or even the drives inside the DataPacs isnĀ“t the best choice at all, because the Controller connects to the DataPacs via a special Cable (provides all necessary Signals and even Power to the drives) and inside the Datapacs the HDDs are connected via a soldered Flat-Flex-Cable to the outer shell of the cartridge; so there seems to be not much what can be done in terms of replacing any hardware.

    So my question is: What else could i try - and , would anybody of you which owns the original PAC 286 Disks be so kind and provide me Image-Files of those Disks? That would be very nice !

    Kind regards

  2. #2


    So far i have managed to get "some" access by using "hardprep" - at least the Controller diagnostics function provided by "Hardprep" does not fail, but any attempt to initialize / performing any HDD access in general leads to a "Drive not ready" error, even if the Parameters of the Drive are recognized correctly.

    Fdisk generally comes up with "no fixed disks present".

    Trying to access the controller Itself by using Debug and g=C800 (and other Adresses/Offsets) does not work either. The Controller seems to be too specific.

  3. #3


    Well, seems to be that the Drives themselfes are really gone.

    So, for Gods sake, I“ve opened one of them and the issue seems to be that the stepper motor isn“t able to move the heads over the head release mechanism (some sort of a plastic "W" shape between the heads) , which is connected via a spring to the head release solenoid. The entire head assembly somehow "bends" itself over to the left, if the stepper motor tries to force the head to the middle, resulting in a audible touching head corner. The head assembly should push the head release mechanism out of the way when its moving forward , but most of the time it isn“t able to do so.

    The head mechanism is only held by one sliding bar on the left, and on the right it is only held down by the gear of the stepper motor. The surface itself is/was good.

  4. #4


    Well, nothing i was expecting. One word: Sh*t.

    If the Top drive has this issue, then the lower drive for sure too.

  5. #5


    Well done, both Drives had Headcrashes (was first invisible due the fact that the surfaces are destroyed on the lower platters) and are of course unusable.

    Since Datapacs are not available at all, and if any of them come up for sale, they are way too expensive (and i assume they will be shipped not with the Heads in Park Position, so another headcrashed Drive can be expected).

    So i assume that the only meaningful way would be to install a IDE Controller. Another MFM Controller with Harddrive would make no sense at all, even too expensive and too risky.

    But the big question is: There are dozens of Multi I/O-Cards with IDE Interface on the Market - does anybody know if they provide a internal BIOS at all, or is a EPROM on the circuit board the only indication ? The Tandon BIOS has no Options for IDE, only MFM or RLL.

  6. #6


    Does the HD setup offer a Type 47 or equivalent (User) selection where you can manually enter the drive's geometry? If so, that should be all you need to configure a (modest) IDE drive. If not, you can most likely 'fudge' it by selecting something close to the IDE drive's actual capacity but maybe a bit smaller. Older, smaller IDE drives tend to conform, to some degree anyway, to the available CMOS selections.
    PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

  7. #7


    Yes, it offers a Type 47, but CHS cannot be entered manually - unfortunaly.

    But i am still happy, if the IDE Controller would be able to work even with predefined CHS-Parameters and my old 8.4GB IDE Drive....would be a great loss of Space, but better than nothing.

    Thank you !

  8. #8


    Maybe i will try a different approach by replacing the Platters of the defect Harddrives by using those of newer drives, if the Diameter at all, the inner hole and their thickness does not differ, which could be quite a challenge to find that out. But im am even not sure if the (perhaps) different coating and its magnetic properties / higher Density could make trouble, since my only knowledge in this term is that old Floppy drives with low capacity can have sometimes trouble with newer high density disks. Maybe that's true here as well.

  9. #9


    Why thinking about that solution: I have the strong feeling that the BIOS of the Computer relies too much on the existence and initial communication to the specific and quite complex RLL controller (or at least something made by Tandon) and could maybe not work together with a ROM-less IDE Controller or even not with a Controller that has its own ROM. Maybe invoking a old Adaptec 1540/1542 and a SCSI HDD could also do the job, but yes, i will first try a ROM-less Multi IO-Card.

  10. #10


    Status: It works with a ROMless Multi/IO-Card very well. The only thing which needed an adjustment was the deactivation of the FDD Controller on this card. No BIOS complaints so far, extra I/O Ports are also usable.

    Since CHS cannot be selected manually (as stated before), maximum usable Size is about 171 MB (Type 9, RLL Mode) of the 8,6 GB Drive. I will later look for a 1 GB HDD in order to keep the loss of capacity smaller.


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